Since it would take quite a patchwork of quotes to summarize this story, I'll just give a few bullet-points of my own as a summary.
- Revision3 uses BitTorrent to distribute its own content (legal distribution, in other words)
- Everybody's second-favorite company MediaDefender decided to play with R3's tracker. Once they found a hole that allowed the tracker to serve torrents not by R3, they began using the tracker to track their own files.
- R3 discovered that somebody was using their tracker for external content and banned MD's torrents
- MD's servers (the ones actually uploading the files that they were using R3's tracker to track) responded by DOSing R3's tracker (according to one person on Slashdot, MD has a 9 Gbps internet connection for this purpose), taking R3's tracker and other systems completely offline
- The FBI is currently investigating the incident. Some have suggested and are praying that the PATRIOT Act could be used to charge MD with cyber-terrorism, as defined by law.
Inside the Attack that Crippled Revision3 (mirror)
MediaDefender, Revision3, screw-up
Revision3 Sends FBI after MediaDefender